1. Field of the Invention
The present invention relates to a graphics display terminal's capability to zoom in on a displayed image.
2. Description of the Prior Art
Graphics display terminals of the prior art possessed a zoom capability whereby a portion of a displayed image could be magnified on a cathode ray tube (CRT) for further display. However, the terminal performed the zoom operation based on the already established pixel representation of the image. The pixel representation of the image would be stored in a memory. The zoom operation was entirely hardware generated. When performing the zoom operation, the hardware would read the pixel data from the memory at rate slower than the rate at which the pixel data was read from the memory when the hardware was not performing the zoom operation. Since the raster scan across the CRT always takes place at the same scan rate, the visual effect of reading the data from the memory at the slower rate, when performing the zoom operation, was an increase in the width of the lines displayed on the CRT. Consequently, if it were desired to perform the zoom operation on a certain small portion of the displayed image, the width of each and every line would increase as a result of the zoom operation. Since the line width increases as a result of the zoom operation, there is a definite limit in the amount or degree to which a displayed image can undergo a zoom operation.